出队列，调用pop_front会不会删除并销毁队头元素

问题背景：
while(!AQueue.empty())
{
    AType *pa = AQueue.front();
    xxx_free(pa->element);//这里是调用私有的free完成必要的释放
    delete pa;
    AQueue.pop_front();
}

针对上述的实现，有个疑问：pop_front会不会删除并销毁队头元素？自
己delete后，再调用pop_front不是会重复释放？


试验程序：myqueue.cpp
#include <iostream>
#include <queue>

class A
{
public:

    A(){std::cout << "A constructor " << '
';}
    ~A(){std::cout << "A destructor " << '
';}

    void fun();
};

void A::fun()
{
    std::cout << "A::fun()" << '
';
}


int main()
{
    std::queue<A> myqueue;
    A a1;
    A a2;
    myqueue.push(a1);
    myqueue.push(a2);

    a1.fun();
    a2.fun();

    myqueue.pop();
    a1.fun();
    a2.fun();

   return 0;
}

编译：g++ -g -Wall -std=c++11 myqueue.cpp

打印：
A constructor
A constructor
A::fun()
A::fun()
A destructor
A::fun()
A::fun()
A destructor
A destructor
A destructor


实验一：修改程序如下
#include <iostream>
#include <queue>

class A
{
public:

    A(){std::cout << "A constructor " << '
';}
    ~A(){std::cout << "A destructor " << '
';}

    void fun();
};

void A::fun()
{
    std::cout << "A::fun()" << '
';
}


int main()
{
    std::queue<A> myqueue;
    A a1;
    //A a2;
    myqueue.push(a1);
    //myqueue.push(a2);

    //a1.fun();
    //a2.fun();

    myqueue.pop();
    a1.fun();
    //a2.fun();

   return 0;
}


打印：
A constructor
A destructor
A::fun()
A destructor


实验二：修改程序如下
#include <queue>

class A
{
public:

    A(){std::cout << "A constructor " << '
';}
    ~A(){std::cout << "A destructor " << '
';}

    void fun();
};

void A::fun()
{
    std::cout << "A::fun()" << '
';
}


int main()
{
    std::queue<A*> myqueue;
    A *pa1 = new A();

    myqueue.push(pa1);
    std::cout << "myqueue push pa1" << '
';

    myqueue.pop();

    pa1->fun();

   return 0;
}


打印：
A constructor
myqueue push pa1
A::fun()
//上面的实验二有内存泄漏，并且没有调用析构函数


实验三：修改程序如下
#include <iostream>
#include <queue>

class A
{
public:

    A(){std::cout << "A constructor " << '
';}
    ~A(){std::cout << "A destructor " << '
';}

    void fun();
};

void A::fun()
{
    std::cout << "A::fun()" << '
';
}


int main()
{
    std::queue<A*> myqueue;
    A *pa1 = new A();

    myqueue.push(pa1);
    std::cout << "myqueue push pa1" << '
';

    std::cout << "before pop myqueue.size()=" << myqueue.size() << '
';
    myqueue.pop();
    std::cout << "after pop myqueue.size()=" << myqueue.size() << '
';

    pa1->fun();

    if(pa1 != nullptr)
    {
        std::cout << "delete pa1" << '
';
        delete pa1;
        pa1 = nullptr;
    }
   return 0;
}


打印：
A constructor
myqueue push pa1
before pop myqueue.size()=1
after pop myqueue.size()=0
A::fun()
delete pa1
A destructor



实验四：修改程序如下
#include <iostream>
#include <queue>

class A
{
public:

    A(){std::cout << "A constructor " << '
';}
    ~A(){std::cout << "A destructor " << '
';}

    void fun();
};

void A::fun()
{
    std::cout << "A::fun()" << '
';
}


int test()
{
    std::queue<A*> myqueue;
    A *pa1 = new A();

    myqueue.push(pa1);
    std::cout << "myqueue push pa1" << '
';

    std::cout << "before pop myqueue.size()=" << myqueue.size() << '
';
    myqueue.pop();
    std::cout << "after pop myqueue.size()=" << myqueue.size() << '
';

    pa1->fun();

    /*if(pa1 != nullptr)
    {
        std::cout << "delete pa1" << '
';
        delete pa1;
        pa1 = nullptr;
    }*/
   return 0;
}

int main()
{
    test();

    std::cout << "test out" << '
';
    return 0;
}

打印：
A constructor
myqueue push pa1
before pop myqueue.size()=1
after pop myqueue.size()=0
A::fun()
delete pa1
A destructor
test out